Deployment And Dragging Control Of Tethered Satellites Based On The Variable Length Cable Model

Tethered satellites system(TSS)are a major mainstream in today's space science research.TSS dynamics modeling and tether deployment and recovery control issues are two major problems in the current research.In this paper,the dynamic modeling and tether stability control methods for TSS deployment and transfer process are studied,including the following aspects:Fully research and analyze the deficiencies in existing solutions,and understand the latest research results of current cable modeling theory and the application prospects of modern control theory in this field.To clarify the importance and necessity of the research on the TSS dynamics modeling method and its retraction control algorithm;Based on absolute nodal coordinate method(ANCF)beam theory,derived considering the variable length cable boundaries with the mass flow velocity.Based on the satellite rigid body dynamic model,the TSS dynamic model with variable length tether is deduced which can accurately reflect the dynamic behavior of tether;In order to study the stability control problem of tether deployment and recycling process,the “dumbbell model” of the TSS is given as the control analysis platform,and it is dimensionless processed to obtain the normalized model of the TSS;The dynamic characteristics of the variable length tether are studied by simulating and analyzing the passive deployment and stabilization process under the gravity gradient of the tether.Then,the dynamic simulation of the thrust,the relative velocity,the relative attitude,and the initial state of the tether are carried out for the transfer process,and the result is qualitatively given.The uniform speed,acceleration and variable acceleration deployment process of the tether were simulated and analyzed.The Gaussian pseudo-spectral method is used to optimize the tether deployment trajectory that meets the control constraints.Based on the sliding mode control theory,the deployment control method which can effectively suppress the tether swing angle is obtained.Aiming at the transfer process of TSS,the transfer orbit is firstly designed according to the time-energy principle.Considered that the TSS only has a single controlled quantity.Based on the layered sliding mode control idea,the control method including the under-actuated state quantity is designed.Finally,the simulation and verification of the tether satellite transfer process are carried out.